Functionally, it works just like an alternative XP system, which brings nothing special to the class, nothing that would add to the TA specialty and mechanics. The levelling requirements are just completely out of touch with the game itself. The only thing that this system brings is thus an obscure and extremely grindy addition to the game, which brings nothing to the class itself.

I am nowhere near your level 125, having so far only managed to level up one weapon to 100. I use 2 vanguards and 3 destroyers in my build, with 2 melee and 2 ranged types of weapons. Two million tech fragments per weapon at level 125 is just absurd. Not because in itself it is a steep mountain to climb, but because we are allowed to climb that mountain slower than snails.

I have been keeping a track of all the tech fragment gains in more than 100 missions, all of them +10 to +12 with some higher levels for experimentation. The average drop rate per mission is 13777 fragments. The highest gain per mission was 33792, which was a level 111 assassination mission against the void brethren in an open map. Apart from that one, I only had one more mission with 30k+ fragments. The lowest number of drops was 4462, which was a level 112 purge mission. Overall I found assassination and callous hunt missions to be the best in terms of tech fragment yields vs time spent in mission.

Mission levels 110 - 112 are the sweet spot for fragments farming, as there are no additional gains from higher level missions. In fact, one of my level 117 experiments yielded only 6596 fragments, which is pathetic. If you're only running the missions for the tech fragments, there is zero reason to go beyond level 110 - 112.

As per @MARCOPOLOCS‍'s clarification, the mission level and the number of enemies (not all of them will drop a fragment, apparently they each have a drop chance) are the only factors that determine the tech fragment drop rates, so there's no method to influence them in any other way. I suspect the tech fragment drop rate update a few weeks ago capped the increase at 700% for all 10+ missions, so it doesn't matter if you run +18 missions, your drop rate will always be limited to 700%.

The system and the levelling pace as it is now is a full time job anywhere beyond levels 100 - 110, I would say. And I do mean full time. Even when I farm 2-3 hours in a day, I now manage to get 1-2 levels and that's at my measly level 100 weapon (I only have one, the rest are level 90 max). If you want a varied gameplay and weapons for your constructs, anything beyond level 100 - 110 is completely unrealistic, unless you are planning to grind this game 8 hours a day for the whole season. Which is pretty pointless, to be perfectly honest, as my constructs manage even level 117 missions with their paltry level 90 weapons just fine.

The tech fragment levelling needs re-thinking, as it just doesn't work the way it is currently implemented.

I copy here a link to the whole spreadsheet with a bit over 100 missions tested. Use filters to have a closer look at different categories.

The best missions for fragments seem to be Void Brethren missions, as they have average drop rate of 17186, vs the global average of 13.7k. However, the Soul Grinder maps are pretty mediocre in terms of tech fragment drops. Without them, the VB mission average would be 19897.

So I would say that as far as the regular missions go, the best tech fragment yield would be from level 110 - 112 Void Brethren assassination missions. They seem to be fairly rare, but if you have plenty of tier 2 insignias, just keep clicking until you get them.

I should probably do some testing of special assignments, including Valorous Heart, to check the tech fragments vs time spent in mission ratio. If I find the will to do it, that is - for now I have moved to different games, as I'm not in the mood to spend days grinding away just to get 1 extra weapon level for one of my construct weapons.

I haven't really played in weeks, tbh. And my build is far from optimal - it manages to beat missions up to +18 to +20 without major issues and since tech fragments farming really requires missions around or a bit over +10, there's not much motivation for me to try min-maxing my build.

Anyway, like Distemper wrote, relic modules are the easiest way to slap some AoE on your single target constructs. The ones below are what you will be looking for (click for a larger version):

However, while running a vivisector build gives you the awesome advantage of having to level up only one weapon (saving you a HUGE grind in later stages), it also means you will not have much room for a more varied modules build. The best dps modules are generally the explode ones (they can literally tear the Soul Grinder to pieces in seconds if there are enough mobs around him) and the 'x% damage bonus for every debuff on the target' (max is 27% per debuff I think).

Most vivisector builds I've seen focus on the TA tanking, while ranged vivisectors do the damage. I haven't seen many melee vivisector builds, they're not very durable to withstand all the melee punishment (+random AoEs) at higher mission levels.

My build is 2x kataphron vanguards and 3x destroyers. I use 1 power axe + 1 greataxe (for variety and GA's extra melee AoE) and grav cannon + phosphor blaster for destroyers. Grav cannon is an absolute beast, tearing through mobs like hot knife through butter, and you can give it AoE (Mass Manipulation in the construct offense tree).

My TA is built as a back-line target designator and debuffer, while constructs do the real work. I use Noospheric targeting, Cull the Weak and Deversive tactics as perks. I don't think they're really optimal, but they're good enough for all the content I run, so I've never really bothered looking into them more deeply. With attributes I am now at 20/20/15.

As a debuffer, the best weapon for me is the plasma caliver alpha (beta for focusing bosses), since it hits enemies next to your target, allowing you to debuff whole groups of mobs in quick succession. You want all your gear rerolled to boost constructs, of course.

All doctrines are also +construct / physical / heat damage. Additional uncreator psalm per item (their effect doesn't stack in the same item) and then armour reducing ones for the annoying heavily armoured missions.

As for construct modules, I use damage reduction, resistances and life leech on my vanguards, as they're always in the biggest mess on the battlefield. You can reroll your relic forcefield module to have up to 8% life regeneration per second (in addition to life leech), which is huge when your vanguard has 15 - 20k+ health. But obviously, as your weapon level goes up, the life leech enchant will be gaining more value.

Destroyers have two dps and one motive modules each - extra dmg per debuff is the biggest dps contributor. Normally it's not necessary to give them survivability modules, as they should not be getting hit too much and it's easy to re-position them if needed (unlike the vanguards, who just charge back into the fray).

In terms of skill trees - all construct-enhancing ones are a priority, obviously. Skip the talents for constructs you don't use. I also use (almost) maxed-out debuff tree and defense, since otherwise it's too easy to get killed in a split second if you don't pay attention for a moment. But otherwise my defenses are not that high, currently at 59/50/36/52. The Aegis Protocol (in Bionics) also helps a bit with that.

That should be it, I suppose. As I said, I don't really play Martyr these days - I'm sure there's plenty of tinkering possible to improve my TA, but even with this fairly generic build missions are easy. Kataphrons are by far my favourite constructs this season and the aggressiveness of the vanguards is just so beautiful to watch. Kataphrons can survive almost anything even in higher level missions, they have excellent dps and generally put great pressure on the enemies. Vanguards' charge also acts as a cc, sometimes knocking down whole groups of enemies (or sending them flying).

Your biggest decision as far as TA class goes will be about which constructs to use. You can go for a more varied build like mine, but you will hit the tech fragments brick wall very fast - with up to six weapons to level up, it just makes no sense to continue the grind with the current system. Or you stick to a vivisector build and will have a much easier time, since they only use a single weapon type. At some point your weapon level will be so high you will faceroll anything.